Clearance rate comparison in second look nephroscopy vs PCNL alone for stones less than 800 hounsfield units. A randomised control trial in Hospital Tengku Ampuan Afzan, Kuantan, Malaysia

Abstract

Residual stones post percutaneous nephrolithotomy (PCNL) are not detected up to 17% on post-operative imaging. Plain radiograph may not detect residual for radiolucent or vague radio opaque stones post-operatively. Our objectives was to determine the incidence of significant residual stones of less than 800HU and whether routine second look nephroscopy improves the clearance rate of PCNL. We conducted a prospective single center randomized control trial from June 2015 to December 2017 in Hospital Tengku Ampuan Afzan, Kuantan, Malaysia, comparing PCNL only with PCNL with second look nephroscopy for stones less than 800HU. Patients were randomized to “PCNL only” or “PCNL with second look nephroscopy”. Both arms are followed up at 3 months with ultrasonography to detect residual. The primary end point was clearance rate of PCNL with second look compared to PCNL only. All enrolled patients, 60 were comparable for age (p = 0.517), gender (p = 0.305), BMI (p = 0.036) and ASA (p = 0.456). Between two groups, mean Hounsfield Unit (HU) were 472 (p = 0.794), duration of op (p = 0.193), and stone size (p = 0.053). At initial, clearance rate of PCNL alone is 80% vs 70% for second look group. Post-operative KUB X-ray detected additional 2 patients in residual in PCNL only group and 5 in the Second Look group. The intervention group (second look nephroscopy) was able to detect 40% more residual stones by which 43% were cleared, the rest were not cleared due to intervention failure and unreachability. Post-operative ultrasound showed residuals in 3 patients who received second look compared with 15 residuals detected on PCNL only, a difference of 58% vs 89% respectively which is statistically significant (p = 0.002; < 0.05). Second look nephroscopy is able to detect missed radiolucent stones post PCNL up to 40% and improve clearance rate of radiolucent stones up to 90% compared to PCNL alone.